Mongo shell repo steps with results: > db.version() 4.2.2 > db.createCollection( 'test_map_ne' )> db.createCollection( 'test_map_ne' ){ "ok" : 1 }> db.test_map_ne.insert([{key: 'one' , val: 1}, {key: 'two' , val: 2}])BulkWriteResult({ "writeErrors" : [ ], "writeConcernErrors" : [ ], "nInserted" : 2, "nUpserted" : 0, "nMatched" : 0, "nModified" : 0, "nRemoved" : 0, "upserted" : [ ]})> db.test_map_ne.find({}){ "_id" : ObjectId( "5df7c48074a7e8d75b9f2ea6" ), "key" : "one" , "val" : 1 }{ "_id" : ObjectId( "5df7c48074a7e8d75b9f2ea7" ), "key" : "two" , "val" : 2 }> db.test_map_ne.find({key: {$ne: 'one' }}){ "_id" : ObjectId( "5df7c48074a7e8d75b9f2ea7" ), "key" : "two" , "val" : 2 }> var mapper = function() {emit( this ._id, this .val);};> var reducer = function(k, v) { return Array.sum(v);};> db.test_map_ne.mapReduce(mapper, reducer, {out: {inline: 1}, query: {}}){ "results" : [ { "_id" : ObjectId( "5df7c48074a7e8d75b9f2ea6" ), "value" : 1 }, { "_id" : ObjectId( "5df7c48074a7e8d75b9f2ea7" ), "value" : 2 } ], "timeMillis" : 24, "counts" : { "input" : 2, "emit" : 2, "reduce" : 0, "output" : 2 }, "ok" : 1}> db.test_map_ne.mapReduce(mapper, reducer, {out: {inline: 1}, query: {key: {$ne: 'one' }}})2019-12-16T19:56:10.707+0200 I  NETWORK  [js] DBClientConnection failed to receive message from 127.0.0.1:27017 - HostUnreachable: Connection closed by peer2019-12-16T19:56:10.707+0200 E  QUERY    [js] uncaught exception: Error: error doing query: failed: network error while attempting to run command 'mapreduce' on host '127.0.0.1:27017'   :DB.prototype.runCommand@src/mongo/shell/db.js:169:19DB.prototype.runReadCommand@src/mongo/shell/db.js:141:12DBCollection.prototype.mapReduce@src/mongo/shell/collection.js:1078:15@(shell):1:1>  Backtrace: ----- BEGIN BACKTRACE ----- { "backtrace" :[{ "b" : "55E96C4B4000" , "o" : "27FFA01" , "s" : "_ZN5mongo15printStackTraceERSo" },{ "b" : "55E96C4B4000" , "o" : "27FF1FE" },{ "b" : "55E96C4B4000" , "o" : "27FF3DC" },{ "b" : "55E96C4B4000" , "o" : "1DFFE74" },{ "b" : "7F74BB793000" , "o" : "F5F0" },{ "b" : "55E96C4B4000" , "o" : "123690C" },{ "b" : "55E96C4B4000" , "o" : "12386B3" , "s" : "_ZN5mongo2mr16MapReduceCommand9errmsgRunEPNS_16OperationContextERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERKNS_7BSONObjERS9_RNS_14BSONObjBuilderE" },{ "b" : "55E96C4B4000" , "o" : "21FD276" , "s" : "_ZN5mongo23ErrmsgCommandDeprecated3runEPNS_16OperationContextERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERKNS_7BSONObjERNS_14BSONObjBuilderE" },{ "b" : "55E96C4B4000" , "o" : "2202DC4" , "s" : "_ZN5mongo12BasicCommand10Invocation3runEPNS_16OperationContextEPNS_3rpc21ReplyBuilderInterfaceE" },{ "b" : "55E96C4B4000" , "o" : "1146498" },{ "b" : "55E96C4B4000" , "o" : "1148984" },{ "b" : "55E96C4B4000" , "o" : "11496EA" , "s" : "_ZN5mongo23ServiceEntryPointCommon13handleRequestEPNS_16OperationContextERKNS_7MessageERKNS0_5HooksE" },{ "b" : "55E96C4B4000" , "o" : "113731C" , "s" : "_ZN5mongo23ServiceEntryPointMongod13handleRequestEPNS_16OperationContextERKNS_7MessageE" },{ "b" : "55E96C4B4000" , "o" : "114389C" , "s" : "_ZN5mongo19ServiceStateMachine15_processMessageENS0_11ThreadGuardE" },{ "b" : "55E96C4B4000" , "o" : "113F09F" , "s" : "_ZN5mongo19ServiceStateMachine15_runNextInGuardENS0_11ThreadGuardE" },{ "b" : "55E96C4B4000" , "o" : "114232C" },{ "b" : "55E96C4B4000" , "o" : "1F45212" , "s" : "_ZN5mongo9transport26ServiceExecutorSynchronous8scheduleESt8functionIFvvEENS0_15ServiceExecutor13ScheduleFlagsENS0_23ServiceExecutorTaskNameE" },{ "b" : "55E96C4B4000" , "o" : "113CA9D" , "s" : "_ZN5mongo19ServiceStateMachine22_scheduleNextWithGuardENS0_11ThreadGuardENS_9transport15ServiceExecutor13ScheduleFlagsENS2_23ServiceExecutorTaskNameENS0_9OwnershipE" },{ "b" : "55E96C4B4000" , "o" : "113FD53" , "s" : "_ZN5mongo19ServiceStateMachine15_sourceCallbackENS_6StatusE" },{ "b" : "55E96C4B4000" , "o" : "113E167" , "s" : "_ZN5mongo19ServiceStateMachine14_sourceMessageENS0_11ThreadGuardE" },{ "b" : "55E96C4B4000" , "o" : "113EFFB" , "s" : "_ZN5mongo19ServiceStateMachine15_runNextInGuardENS0_11ThreadGuardE" },{ "b" : "55E96C4B4000" , "o" : "114232C" },{ "b" : "55E96C4B4000" , "o" : "1F4567B" },{ "b" : "55E96C4B4000" , "o" : "2589454" },{ "b" : "7F74BB793000" , "o" : "7E65" },{ "b" : "7F74BB3C5000" , "o" : "FE88D" , "s" : "clone" }], "processInfo" :{ "mongodbVersion" : "4.2.2" , "gitVersion" : "a0bbbff6ada159e19298d37946ac8dc4b497eadf" , "compiledModules" : [], "uname" : { "sysname" : "Linux" , "release" : "3.10.0-1062.4.3.el7.x86_64" , "version" : "#1 SMP Wed Nov 13 23:58:53 UTC 2019" , "machine" : "x86_64" }, "somap" : [ { "b" : "55E96C4B4000" , "elfType" : 3, "buildId" : "67F0B211856C5980A144552C72D5392B3453718F" }, { "b" : "7FFE5D811000" , "elfType" : 3, "buildId" : "9EAE8893CACF7C03FAC2CEED330551A226918061" }, { "b" : "7F74BCBC1000" , "path" : "/lib64/libcurl.so.4" , "elfType" : 3, "buildId" : "89C83CEB5DE5FDEC4F3DFBA4FCAACB53D747A998" }, { "b" : "7F74BC9A8000" , "path" : "/lib64/libresolv.so.2" , "elfType" : 3, "buildId" : "3009B26B33156EAAF99787AA3DA0C6AE99649755" }, { "b" : "7F74BC545000" , "path" : "/lib64/libcrypto.so.10" , "elfType" : 3, "buildId" : "4CF1939F660008CFA869D8364651F31AACD2C1C4" }, { "b" : "7F74BC2D3000" , "path" : "/lib64/libssl.so.10" , "elfType" : 3, "buildId" : "3B305C3BA17FE394862E749763F2956C9C890C2E" }, { "b" : "7F74BC0CF000" , "path" : "/lib64/libdl.so.2" , "elfType" : 3, "buildId" : "18113E6E83D8E981B8E8D808F7F3DBB23F950A1D" }, { "b" : "7F74BBEC7000" , "path" : "/lib64/librt.so.1" , "elfType" : 3, "buildId" : "4749697BF078337576C4629F0D30B296A0939779" }, { "b" : "7F74BBBC5000" , "path" : "/lib64/libm.so.6" , "elfType" : 3, "buildId" : "5681C054FDABCF789F4DDA66E94F1F6ED1747327" }, { "b" : "7F74BB9AF000" , "path" : "/lib64/libgcc_s.so.1" , "elfType" : 3, "buildId" : "DAC0179F4555AEFEC9E97476201802FD20C03EC5" }, { "b" : "7F74BB793000" , "path" : 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"path" : "/lib64/libcom_err.so.2" , "elfType" : 3, "buildId" : "67E935BFABA2C914C01156B88947DD515EA51170" }, { "b" : "7F74B93C2000" , "path" : "/lib64/liblber-2.4.so.2" , "elfType" : 3, "buildId" : "3192C56CD451E18EB9F29CB045432BA9C738DD29" }, { "b" : "7F74B916D000" , "path" : "/lib64/libldap-2.4.so.2" , "elfType" : 3, "buildId" : "F1FADDDE0D21D5F4E2DCADEDD3B85B6E7AAC9883" }, { "b" : "7F74B8F57000" , "path" : "/lib64/libz.so.1" , "elfType" : 3, "buildId" : "B9D5F73428BD6AD68C96986B57BEA3B7CEDB9745" }, { "b" : "7F74B8D47000" , "path" : "/lib64/libkrb5support.so.0" , "elfType" : 3, "buildId" : "4F5FBB2087BE132892467C4E7A46A3D07E5DA40B" }, { "b" : "7F74B8B43000" , "path" : "/lib64/libkeyutils.so.1" , "elfType" : 3, "buildId" : "2E01D5AC08C1280D013AAB96B292AC58BC30A263" }, { "b" : "7F74B8926000" , "path" : "/lib64/libsasl2.so.3" , "elfType" : 3, "buildId" : "E2F2017F821DD1B9D307DA1A9B8014F2941AEB7B" }, { "b" : "7F74B86FF000" , "path" : "/lib64/libselinux.so.1" , "elfType" : 3, "buildId" : "D2DD4DA3FDE1477D25BFFF80F3A25FDB541A8179" }, { "b" : "7F74B84C8000" , "path" : "/lib64/libcrypt.so.1" , "elfType" : 3, "buildId" : "84467C988F41D853C58353BEB247670E15DA8BAD" }, { "b" : "7F74B8266000" , "path" : "/lib64/libpcre.so.1" , "elfType" : 3, "buildId" : "9CA3D11F018BEEB719CDB34BE800BF1641350D0A" }, { "b" : "7F74B8063000" , "path" : "/lib64/libfreebl3.so" , "elfType" : 3, "buildId" : "197680DAE6538245CB99723E57447C4EF2E98362" } ] }} mongod(_ZN5mongo15printStackTraceERSo+0x41) [0x55e96ecb3a01] mongod(+0x27FF1FE) [0x55e96ecb31fe] mongod(+0x27FF3DC) [0x55e96ecb33dc] mongod(+0x1DFFE74) [0x55e96e2b3e74] libpthread.so.0(+0xF5F0) [0x7f74bb7a25f0] mongod(+0x123690C) [0x55e96d6ea90c] mongod(_ZN5mongo2mr16MapReduceCommand9errmsgRunEPNS_16OperationContextERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERKNS_7BSONObjERS9_RNS_14BSONObjBuilderE+0x6B3) [0x55e96d6ec6b3] mongod(_ZN5mongo23ErrmsgCommandDeprecated3runEPNS_16OperationContextERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERKNS_7BSONObjERNS_14BSONObjBuilderE+0x46) [0x55e96e6b1276] mongod(_ZN5mongo12BasicCommand10Invocation3runEPNS_16OperationContextEPNS_3rpc21ReplyBuilderInterfaceE+0x74) [0x55e96e6b6dc4] mongod(+0x1146498) [0x55e96d5fa498] mongod(+0x1148984) [0x55e96d5fc984] mongod(_ZN5mongo23ServiceEntryPointCommon13handleRequestEPNS_16OperationContextERKNS_7MessageERKNS0_5HooksE+0x41A) [0x55e96d5fd6ea] mongod(_ZN5mongo23ServiceEntryPointMongod13handleRequestEPNS_16OperationContextERKNS_7MessageE+0x3C) [0x55e96d5eb31c] mongod(_ZN5mongo19ServiceStateMachine15_processMessageENS0_11ThreadGuardE+0xEC) [0x55e96d5f789c] mongod(_ZN5mongo19ServiceStateMachine15_runNextInGuardENS0_11ThreadGuardE+0x17F) [0x55e96d5f309f] mongod(+0x114232C) [0x55e96d5f632c] mongod(_ZN5mongo9transport26ServiceExecutorSynchronous8scheduleESt8functionIFvvEENS0_15ServiceExecutor13ScheduleFlagsENS0_23ServiceExecutorTaskNameE+0x182) [0x55e96e3f9212] mongod(_ZN5mongo19ServiceStateMachine22_scheduleNextWithGuardENS0_11ThreadGuardENS_9transport15ServiceExecutor13ScheduleFlagsENS2_23ServiceExecutorTaskNameENS0_9OwnershipE+0x10D) [0x55e96d5f0a9d] mongod(_ZN5mongo19ServiceStateMachine15_sourceCallbackENS_6StatusE+0x843) [0x55e96d5f3d53] mongod(_ZN5mongo19ServiceStateMachine14_sourceMessageENS0_11ThreadGuardE+0x2E7) [0x55e96d5f2167] mongod(_ZN5mongo19ServiceStateMachine15_runNextInGuardENS0_11ThreadGuardE+0xDB) [0x55e96d5f2ffb] mongod(+0x114232C) [0x55e96d5f632c] mongod(+0x1F4567B) [0x55e96e3f967b] mongod(+0x2589454) [0x55e96ea3d454] libpthread.so.0(+0x7E65) [0x7f74bb79ae65] libc.so.6(clone+0x6D) [0x7f74bb4c388d] ----- END BACKTRACE -----